Helideck Design for Offshore Platforms

Understanding Helideck Design for Offshore Platforms

Offshore platform operations in the demanding waters of the North Atlantic require robust, reliable helicopter landing facilities that can withstand extreme environmental conditions while ensuring the safety of personnel and aircraft. Helideck design represents one of the most critical aspects of offshore engineering, combining structural integrity, aerodynamic considerations, and stringent regulatory compliance into a single integrated system.

For operators working in Atlantic Canada's offshore energy sector, including the Sable Offshore Energy Project area and emerging developments off Nova Scotia's coastline, helideck design must account for the region's challenging weather patterns, including fog, icing conditions, and significant wave heights that can exceed 15 metres during winter storms. This comprehensive guide explores the essential elements of helideck design and the engineering considerations that ensure safe, efficient helicopter operations throughout the year.

Regulatory Framework and Design Standards

Helideck design in Canadian waters falls under multiple regulatory jurisdictions, requiring engineers to navigate a complex landscape of national and international standards. The primary governing documents include:

• Canadian Aviation Regulations (CARs) – Transport Canada's requirements for heliport design and operation

• Canada-Nova Scotia Offshore Petroleum Board (CNSOPB) guidelines for offshore installations

• CAP 437 – The UK Civil Aviation Authority's offshore helicopter landing areas standards, widely adopted internationally

• ICAO Annex 14, Volume II – International Civil Aviation Organisation heliport design standards

• API RP 2L – American Petroleum Institute recommended practices for helideck design

• ISO 19901-3 – International standards for topsides structure design

Canadian offshore operators typically require helidecks to meet or exceed CAP 437 standards, which have become the de facto international benchmark for offshore helicopter operations. These standards specify minimum dimensions, obstacle clearance requirements, structural load criteria, and safety equipment provisions that form the foundation of any helideck design project.

Classification Society Requirements

Beyond aviation regulations, helidecks on offshore structures must satisfy classification society rules from organisations such as Lloyd's Register, DNV, Bureau Veritas, or the American Bureau of Shipping. These rules address structural design methodology, material specifications, fatigue analysis requirements, and inspection protocols that ensure long-term operational integrity in the harsh marine environment.

Structural Design Considerations

The structural engineering of an offshore helideck presents unique challenges that require careful analysis and robust design solutions. Engineers must consider multiple load cases and their combinations to develop a structure capable of safely supporting helicopter operations under all anticipated conditions.

Design Loads and Load Combinations

Helideck structural design must account for several categories of loading:

• Helicopter landing loads – Dynamic impact factors typically range from 1.5 to 2.5 times the maximum take-off weight (MTOW), depending on the design standard applied

• Emergency landing loads – Crash landing scenarios require consideration of loads up to 2.5 times MTOW with appropriate distribution patterns

• Dead loads – Self-weight of structural members, deck plating, fire protection systems, and permanent equipment

• Live loads – Personnel, portable equipment, and maintenance activities, typically specified at 2.0 to 4.0 kN/m²

• Environmental loads – Wind, wave-induced motions, snow accumulation, and ice accretion particular to Maritime Canada's climate

For installations in Nova Scotia's offshore waters, ice accretion loading deserves particular attention. Freezing spray and precipitation can accumulate ice loads of 30 to 50 kg/m² on exposed surfaces during winter operations, significantly affecting structural design and requiring robust de-icing capabilities.

Material Selection and Corrosion Protection

Material selection for offshore helidecks must balance structural performance with corrosion resistance in the aggressive marine atmosphere. Common approaches include:

• Structural steel – Typically Grade 350W or equivalent, with comprehensive coating systems including zinc-rich primers, epoxy intermediate coats, and polyurethane topcoats

• Aluminium alloys – Marine-grade 5000 and 6000 series alloys offer excellent corrosion resistance and reduced weight, particularly beneficial for helidecks on floating production systems

• Stainless steel – Duplex grades such as 2205 for critical components requiring superior corrosion resistance

Coating systems for Atlantic Canada applications should provide minimum dry film thicknesses of 350 to 450 micrometres, with particular attention to edge protection and areas susceptible to mechanical damage during helicopter operations.

Dimensional Requirements and Obstacle Clearance

Helideck sizing directly correlates with the largest helicopter type intended to use the facility. The fundamental dimension is the 'D' value, representing the largest overall dimension of the helicopter with rotors turning. For common offshore helicopter types operating in Atlantic Canada:

• Sikorsky S-92 – D value of 20.88 metres, requiring a minimum helideck diameter of 22.86 metres

• Leonardo AW139 – D value of 16.66 metres, requiring a minimum helideck diameter of 18.33 metres

• Sikorsky S-76 – D value of 16.00 metres, requiring a minimum helideck diameter of 17.60 metres

CAP 437 specifies that the touchdown and lift-off area (TLOF) must have a minimum diameter of 1.0 times D, with the load-bearing surface extending to at least 0.83 times D. The helideck perimeter typically extends to 1.0 to 1.25 times D to provide adequate safety margins.

Obstacle-Free Sector and Limited Obstacle Sector

Safe helicopter approach and departure require carefully managed airspace around the helideck. Design must incorporate:

• Obstacle-Free Sector (OFS) – A minimum 210-degree sector free of obstacles above helideck level, oriented into the prevailing wind direction

• Limited Obstacle Sector (LOS) – The remaining 150-degree sector where obstacles are permitted but must not penetrate a surface rising at 1:2 gradient from the helideck edge

• Falling gradient – A 5:1 slope extending outward from the helideck edge within the OFS, which no obstacle should penetrate

For offshore Nova Scotia installations, the OFS orientation must consider predominant wind patterns, which typically favour southwesterly to westerly directions during summer months and northwesterly to northerly directions during winter operations.

Safety Systems and Equipment

Modern helideck design integrates numerous safety systems that protect personnel, aircraft, and the installation itself. These systems require careful coordination during the design phase to ensure proper functionality and accessibility.

Fire Suppression Systems

Helideck fire protection systems must be capable of controlling and extinguishing aviation fuel fires rapidly. Design requirements include:

• Foam fire suppression – Minimum discharge rate of 6 litres/m²/minute of Aqueous Film-Forming Foam (AFFF) concentrate at 3% proportioning

• Deck-integrated deluge systems – Coverage of the entire TLOF area with overlapping spray patterns

• Monitor stations – Typically two to four strategically positioned foam monitors with minimum discharge rates of 750 litres/minute

• Foam inventory – Sufficient concentrate for minimum 10 minutes of continuous discharge, typically 2,000 to 5,000 litres depending on helideck size

Lighting and Visual Aids

Helideck lighting enables safe operations during darkness and reduced visibility conditions common in Maritime Canada. Required lighting systems include:

• Perimeter lighting – Green omnidirectional lights at maximum 3-metre spacing around the helideck edge

• Floodlighting – Minimum 10 lux average illumination across the TLOF with uniformity ratio not exceeding 8:1

• Status lights – Red warning lights indicating helideck availability

• Touchdown marking lighting – Illuminated 'H' marking for night identification

• Approach guidance – Visual approach slope indicators where required by operational considerations

Helicopter Tie-Down and Refuelling Systems

Design must accommodate helicopter securing requirements and, where specified, refuelling operations. Tie-down points should be rated for minimum 50 kN ultimate load capacity and positioned to suit the wheel/skid configurations of intended helicopter types. Refuelling systems, when included, require careful integration of fuel storage, pumping equipment, grounding systems, and spill containment measures.

Environmental and Aerodynamic Considerations

The aerodynamic environment surrounding an offshore helideck significantly affects helicopter handling characteristics and pilot workload. Wind flow patterns created by platform structures can generate turbulence, updrafts, and downdrafts that challenge even experienced pilots.

Wind Flow Analysis

Contemporary helideck design employs Computational Fluid Dynamics (CFD) modelling to analyse wind flow patterns and identify potential hazards. These studies examine:

• Turbulence intensity – Acceptable levels typically below 15% for safe operations

• Vertical velocity components – Downdrafts exceeding 1.75 m/s can significantly affect helicopter performance

• Wind shear gradients – Rapid velocity changes across the approach path create handling difficulties

• Recirculation zones – Areas of reversed flow that can affect rotor performance

For platforms operating in Atlantic Canada's frequently gusty conditions, wind tunnel testing may supplement CFD analysis to validate predicted flow characteristics and identify mitigation measures such as wind walls or porous screens.

Exhaust Gas Considerations

Hot exhaust gases from turbines, flares, and other platform equipment pose significant hazards to helicopter operations. Temperature rises exceeding 2°C above ambient at helideck level can affect engine performance, while visible exhaust plumes create visual obscuration. Design coordination must ensure adequate separation between exhaust sources and helicopter approach paths, often requiring exhaust trajectory modelling under various wind conditions.

Helideck Integration with Platform Design

Successful helideck design requires early integration with overall platform architecture. Key coordination aspects include:

• Structural support – Helideck support structures must interface efficiently with primary platform framing while accommodating thermal expansion and platform motions

• Access and egress – Passenger and crew routes from the helideck to accommodation areas should be direct, protected from weather, and free of trip hazards

• Emergency evacuation – Helideck positioning relative to lifeboats and escape routes affects emergency response planning

• Crane operations – Coordination of helideck operations with cargo transfer activities requires careful scheduling and physical separation

The helideck elevation relative to sea level affects both wave-induced motions and obstacle clearance considerations. Higher elevations reduce motion accelerations but may introduce airflow complications from platform structures below.

Inspection, Maintenance, and Life Extension

Helideck design must facilitate ongoing inspection and maintenance activities throughout the platform's operational life. Design provisions should include:

• Access for inspection – Platforms, walkways, and access hatches enabling close-up examination of structural connections and critical components

• Drainage systems – Proper drainage prevents water accumulation and associated corrosion, ice formation, and slipping hazards

• Sacrificial coatings – Initial coating systems with planned maintenance intervals aligned with platform inspection schedules

• Retrofit provisions – Design flexibility accommodating future helicopter type changes or regulatory requirement updates

For aging helidecks in Atlantic Canada, structural assessment programmes should evaluate fatigue damage accumulation, corrosion degradation, and compliance with current standards to support safe continued operation or identify necessary upgrades.

Partner with Sangster Engineering Ltd. for Your Helideck Design Needs

Designing helidecks for offshore platforms demands specialised expertise combining structural engineering, aviation requirements, and marine environmental considerations. At Sangster Engineering Ltd., our team brings extensive experience in offshore engineering projects throughout Atlantic Canada, understanding the unique challenges presented by our region's demanding operating environment.

From conceptual design through detailed engineering and construction support, we provide comprehensive helideck engineering services tailored to your project requirements. Our familiarity with CNSOPB regulatory processes, combined with strong relationships with classification societies and aviation authorities, ensures your helideck design achieves approval efficiently while meeting the highest safety standards.

Contact Sangster Engineering Ltd. today to discuss your offshore helideck design requirements. Our Amherst, Nova Scotia office serves clients throughout the Maritime provinces and beyond, delivering professional engineering solutions that keep your operations flying safely.

Partner with Sangster Engineering

At Sangster Engineering Ltd. in Amherst, Nova Scotia, we bring decades of engineering experience to every project. Serving clients across Atlantic Canada and beyond.

Contact us today to discuss your engineering needs.